1. Field of the Invention
The present invention relates to a muffler to be coupled to the exhaust pipe of an internal combustion engine for attenuating exhaust sound.
2. Description of the Relevant Art
Generally, the exhaust system of an internal combustion engine is coupled to an exhaust muffler having an expansion chamber. Exhaust gases from the engine are introduced into the expansion chamber and allowed to expand therein for dissipate the energy of the exhaust gases to dampen the exhaust sound.
U.S. Pat. No. 4,589,516, assigned to the same assignee as the assignee of the present application, discloses a muffler comprising a tubular outer box defining an expansion chamber therein and composed of a pair of lateral separate bodies of a formed sound insulation material. A tubular exhaust pipe is inserted into the outer box and bonded thereto by an adhesive. Each of the separate bodies comprises an outer layer of synthetic resin and an inner heat insulation layer of glass wool or the like.
The outer box has a recess of circular cross section in which the exhaust pipe is fitted. When the outer box is subjected to a circumferential rotative force, such a force or moment is limited only by frictional forces between the outer box and the exhaust pipe and also by the bonding strength of the adhesive applied therebetween. Since the bonding strength is reduced with time, the outer box may eventually be caused to rotate with respect to the exhaust pipe when a moment is applied to the outer box about the exhaust pipe.
The present invention has been made to improve the conventional muffler of the type described above.